With the advance of medical sciences, it has become possible to treat a patient's blood in closed-loop processes, returning the patient's own treated blood back to him in one medical treatment. An example of such processes include external treatment methods for diseases in which there is a pathological increase of lymphocytes, such as cutaneous T-cell lymphoma or other diseases affecting white blood cells. In such methods, the patient's blood is irradiated with ultraviolet light in the presence of a chemical or an antibody. Ultraviolet light affects the bonding between the lymphocytes and the chemical or antibody that inhibits the metabolic processes of the lymphocytes.
During one of these medical treatments, a centrifuge bowl, such as, for example, a Latham bowl, as shown in U.S. Pat. No. 4,303,193, expressly incorporated by reference in its entirety herein, separates blood into red blood cells (“RBCs”) and buffy coat. The Latham bowl is a blood component separator that has been used for some time in the medical apheresis market as well as in innovative medical therapies such as extracorporeal photopheresis (ECP). PCT Applications WO 97/36581 and WO 97/36634, and U.S. Pat. Nos. 4,321,919; 4,398,906; 4,428,744; and 4,464,166 provide descriptions of extracorporeal photopheresis, and are hereby expressly incorporated by reference in their entirety.
The Latham bowl efficiency is often measured by the white blood cell (“WBC”) “yield,” which is typically about 50%. Yield is defined as the percentage of cells collected versus the number processed. When compared to other types of whole blood separators, this high yield enables the Latham bowl separator to collect much larger volumes of WBCs while processing much less whole blood from the donor patient. However, a major drawback to the Latham bowl separator is that the separation process must be repeatedly stopped to remove the packed RBCs and plasma once they fill the inside of the bowl, creating a “batch-type” process. Although the Latham bowl separator has a high volume yield, the constant filling and emptying of this bowl wastes time; thus, the process is considered less efficient with respect to time. Additionally, the Latham bowl requires a rotating seal, which is expensive and difficult to manufacture.
An additional drawback of centrifugal processing apparatus has been their high cost of manufacture due to strict tolerances, rotating seals, and extensive manufacturing processes.